Effects Of Combined Application Of Nitrogen And Potassium On Accumulation And Transport Of Dry Matter,and Quality Of Rice

Rice is one of the major food crops in China,and more than half of the population feeds on rice as a staple.Rice provides a lot of energy and rich nutrients for life activities,and is an important cornerstone for the health of the nation’s life.In recent years,with the substantial improvement of the living standard of residents,people have put forward higher requirements for rice quality.Reasonable fertilization is one of the important agronomic technical measures to improve the quality of rice,and nitrogen and potassium are essential macronutrients for the growth and development of rice,which are directly or indirectly affected the growth and development of rice and the formation of yield and quality.The main rice production areas in southern China are deficient in nitrogen and potassium nutrients,but it is common to emphasize the application of nitrogen fertilizer and neglect the application of potassium fertilizer in rice production,and it is of great significance to study the effect of combined application of N and K on rice yield and quality.In this paper,we studied the effects of combined application of N and K on dry matter accumulation and transport characteristics,grain-filling characteristics and the quality formation of rice,based on a Two-year field experiment with Shengiangyou 5814（SLY 5814,hybrid rice）and Xiadao No.1（XD No.1,indica rice）as materials,with a view to provide theoretical basis for the rational application of N and K fertilizer in rice production.The main results are as follows:（1）The combined application of N and K promoted post-flowering stem and leaf dry matter translocation,increased maximum grain-filling rate of inferior grains,maximum theoretical grain weight and crude protein accumulation of superior and inferior grains.N and K combined application(N₁₈₀K₁₂₀)compared with the treatment with N alone(N₁₈₀K₀),the SLY 5814,post-flowering stem and leaf dry matter transfer increased by 633.9 kg/hm²,with the increase rate of 39.96%;the maximum grain-filling rate of inferior grains increased by 0.07 mg/grain/d,with the increase rate of 9.86%;the theoretical maximum grain weight of superior and inferior grains increased by 1.05 mg/grain and 1.07 mg/grain,with increases of 4.57%and 4.85%,respectively.The XD No.1 variety followed the same regularity as SLY 5814,the increases in post-flowering stem and leaf dry matter translocation,maximum grain-filling rate of inferior grains,and theoretical maximum grain weight of superior and inferior grains were 26.24%,14.29%,6.73%,and 8.82%,respectively.N and K combined application compared with the treatment with K alone(N₀K₁₂₀),the SLY 5814,post-flowering stem and leaf dry matter translocation increased by 1067.7 kg/hm²,with the increase rate of 92.64%;the maximum grain-filling rates of superior and inferior grains increased by 0.06 mg/grain/d and 0.07 mg/grain/d,respectively,with increases of 3.80%and 9.86%,respectively;the theoretical maximum grain weight of superior and inferior grains increased by 0.26 mg/grain and 2.28 mg/grain,respectively,with increases of 1.09%and 10.95%,respectively;the crude protein accumulation of superior and inferior grains increased by 0.54 mg/grain and 0.46 mg/grain,respectively,with increases of 39.93%and43.63%,respectively.The XD No.1 variety followed the same regularity as SLY 5814,the increases in post-flowering stem and leaf dry matter translocation,maximum grain-filling rate of superior and inferior grains,theoretical maximum grain weight of superior and inferior grains,and crude protein accumulation of superior and inferior grains were 81.19%,3.03%and 2.56%,1.45%and 8.72%,57.90%and 55.22%,respectively.（2）The combined application of N and K fertilizer significantly improved rice yield and fertilizer utilization.Compared to the N₁₈₀K₀ treatment,the N₁₈₀K₁₂₀ treatment SLY5814 variety for two years in 2020 and 2021,rice yield increased by 1.38 t/hm² and 2.19t/hm²,with the increases of 26.60%and 43.45%,respectively;and the utilization rate of nitrogen fertilizer increased by 10.99 percentage points and 8.16 percentage points,respectively.The varieties of XD No.1 in 2020 and 2021,rice yield increased by 2.22 t/hm²and 2.35 t/hm²,with the increases of 47.20%and 53.60%,respectively,and the utilization rate of nitrogen fertilizer increased by 7.53 percentage points and 9.32 percentage points,respectively.Compared with the N₀K₁₂₀ treatment,the N₁₈₀K₁₂₀ treatment SLY 5814 variety for two years in 2020 and 2021,rice yield increased by 1.00 t/hm² and 1.26 t/hm²,respectively,with the increases of 17.62%and 24.30%,respectively;the utilization rate of potassium fertilizer increased by 14.48 percentage points and 14.87 percentage points,respectively.The varieties of XD No.1 in 2020 and 2021,rice yield increased by 0.80 t/hm²and 1.26 t/hm²,respectively,with the increases of 14.07%and 24.30%,respectively;the utilization rate of potassium fertilizer increased by 10.90 percentage points and 8.26percentage points,respectively.（3）The combined application of N and K significantly improved the head milled rice rate,reduced the chalkiness grain rate and chalkiness degree,increased the crude protein content of milled rice,and improved the comprehensive score of rice taste value.Compared to the N₁₈₀K₀ treatment,the N₁₈₀K₁₂₀ treatment SLY 5814 variety for two years in 2020 and2021,the head milled rice rate increased by 4.81 percentage points and 4.11 percentage points respectively,and the comprehensive score of rice taste value increased by 8.7 points and 4.4 points respectively.The varieties of XD No.1 in 2020 and 2021,the head milled rice rate increased by 5.50 percentage points and 8.69 percentage points respectively,and the comprehensive score of rice taste value increased by 5.7 points and 5.5 points respectively.Compared to the N₀K₁₂₀ treatment,the N₁₈₀K₁₂₀ treatment SLY 5814 variety for two years in 2020 and 2021,the head milled rice rate increased by 8.22 percentage points and 10.67 percentage points respectively,the chalkiness grain rate decreased by 1.13and 1.78 percentage points,the chalkiness degree decreased by 0.70 and 0.63 percentage points,the crude protein content of milled rice increased by 2.17 and 1.83 percentage points,and the comprehensive score of rice taste value decreased by 12.2 and 15.3 points,respectively.The varieties of XD No.1 in 2020 and 2021,the head milled rice rate increased by 5.70 percentage points and 10.90 percentage points respectively,the chalkiness grain rate decreased by 0.77 and 1.51 percentage points,the chalkiness degree decreased by 0.83and 1.06 percentage points,the crude protein content of milled rice increased by 2.60 and2.07 percentage points,and the comprehensive score of rice taste value decreased by 10.9and 11.0 points,respectively.The correlation results showed that the dry matter accumulation of stem and leaves at flowering stage was significantly and positively correlated with the percentage of head milled rice;the nitrogen accumulation of stem and leaves at flowering stage was highly significantly and negatively correlated with the chalkiness grain rate;the theoretical maximum protein accumulation of superior and inferior grains were highly significantly and positively correlated with both rice hardness and crude protein content of milled rice,and were highly and negatively correlated with the comprehensive score of rice taste value.In summary,the combined application of N and K promoted pre-flowering accumulation and post-flowering transfer of dry matter in rice stems and leaves,promoted grain filling and crude protein accumulation in grain,increased rice yield and fertilizer utilization,and significantly improved rice milling,appearance,taste and nutritional quality.